[gdal-dev] GDAL Erdas LAN/GIS driver

[Roger Bivand]

On Mon, 24 Aug 2009, Frank Warmerdam wrote:

> Roger Bivand wrote:
>> 
>> (reverting to list)
>> 
>> Correction, the user reported that:
>> 
>>> Apparently, gdalinfo retrieves the correct min, max, and statistics, 
>>> despite the use of GDT_Int16.
>> 
>> on his Windows platform. The different GDAL versions ought to explain why 
>> his gdalinfo says Int16 but gives statistics from UInt16.
> ...
>> On the trunk, GDT_Int16 is used too, so how does gdalinfo detect that it is 
>> actually UInt16?
>
> Roger,
>
> I believe the min/max is actually being read from the file header in trunk
> and is handled without regard to the actual imagery or it's type.
>
> I skimmed the changelog for this driver and I didn't notice any obvious
> changes in metadata / statistics handling so I'm surprised at this result.
>
> Best regards,
>

Frank,

Having at last got the data and a current 1.7.0dev, I have to report that 
on x86 Linux, I cannot reproduce the reading of Int16 as UInt16 reported 
by the original questioner - I get Int16 and a negative minimum with 
gdalinfo, and in rgdal using the same *.so. How the difference arose is 
unclear, I can download FWTools and check on Windows.

I would argue for replacing Int16 by UInt16 in the LAN/GIS driver based on 
PCI and ESRI references to the data types as unsigned, but am open to 
other arguments.

Best wishes,

Roger

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no